Makefile: GENDOC_INNER: don't create subdirs for generated manuals

The output files are generated directly in $(O)/docs/manual.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

Makefile

@@ -719,7 +719,7 @@ $(1)-$(3): $$(O)/docs/$(1)/$(1).$(4)
 
 $$(O)/docs/$(1)/$(1).$(4): docs/$(1)/$(1).txt $$($(call UPPERCASE,$(1))_SOURCES)
 	@echo "Generating $(5) $(1)..."
-	$(Q)mkdir -p $$(O)/docs/$(1)/$(2)
+	$(Q)mkdir -p $$(@D)
 	$(Q)a2x $(6) -f $(2) -d book -L -r $(TOPDIR)/docs/images \
 	  -D $$(@D) $$<
 endef